The present invention relates to semiconductor devices and a method of manufacturing a semiconductor device.
In the field of semiconductor elements such as horizontal power MISFETs, there is demand for enhanced drain withstand voltage. Drain withstand voltage is evaluated according as whether there occurs characteristics variation or breakdown in a semiconductor element when a rated voltage is continuously applied to the drain electrode with gate voltage off. Characteristics variation or breakdown which occurs in a semiconductor element when a voltage is applied to the drain electrode is attributable to electric field concentration in the semiconductor element caused by the application of the drain voltage. Such electric field concentration easily occurs under the drain side end of the gate electrode.
Electric field concentration which occurs in the semiconductor element due to the application of drain voltage can be reduced, for example, by the use of a field plate electrode. Several techniques relating to semiconductor devices with field plate electrodes as described below have been known.
Japanese Unexamined Patent Publications No. 2011-71307 and No. 2004-200248 disclose that the gate electrode has an eave-like field plate portion. Japanese Unexamined Patent Publications No. 2006-253654, Hei 7 (1995)-321312, and 2008-263140 disclose that a field plate electrode located between a gate electrode and a drain electrode is coupled to a source electrode. Japanese Unexamined Patent Publication No. 2004-214471 discloses that an electric field control electrode located between a gate electrode and a drain electrode is controlled independently of the gate electrode.